Kinda related to your line of questioning Cihan... I just had my first issue ever with purchasing a card from Ebay.com to be shipped to my COMC account. As confirmed above, you can't add a non-Australian address to an Australian PayPal account - makes sense. My PayPal address has my billing address and my Ebay account has several shipping addresses, including my COMC account. I just won a card on Ebay.com (seller accepted my offer) but when I tried to pay for it (process the order), the order simply won't process and remain as unpaid. I contacted the seller to see if he would accept payment from my PayPal, but wants the address to be the same - which it won't be of course. In the process of sorting it out now, but looks like the seller will either agree to cancel the order or I will pay the o/s shipping price and get it sent to my Australian address - completely defeating the purpose of having a COMC account! It's been a couple of months since I've bought a card this way.. but looks like Ebay or PayPal (or both?) have changed the rules slightly. Not sure. I've been doing this for years now and never had a problem.
Not sure if the order of address' in your Ebay account matters... my COMC has always been a secondary address without problems. Hopefully you can get your COMC account setup and working ok soon enough!
Cheers
Andrew